Porous thermally insulating compositions containing hollow silica particles
A thermally insulating composition comprising hollow spherical silica particles and a coating of a material having a thermal conductivity of less than 0.3 W/m·K on surfaces of said silica particles. In particular embodiments, the low conductivity coating material may be a polymer, such as polystyrene or polyvinylpyrrolidone, or the low conductivity coating material may be a quaternary ammonium salt of the Formula (1), i.e., R 1 R 2 R 3 R 4 N + A − , with at least one of R 1 , R 2 , R 3 , and R 4 being an alkyl group containing at least ten carbon atoms (and A − is a counter anion), or the low conductivity coating material may be phenyl-C61-butyric acid methyl ester covalently bound to the hollow spherical silica particles. Also described herein is a method of thermally insulating a surface by applying a coating of the thermally insulating composition, described above, onto the surface.
1. A thermally insulating composition comprising hollow spherical silica particles and a coating material having a thermal conductivity of no more than 0.3 W/m·K on surfaces of said hollow spherical silica particles, wherein said coating material is selected from at least one of the following:
(i) polymers selected from polystyrene or polyvinylpyrrolidinone;
(ii) quaternary ammonium salt having the following formula:
wherein R 1 , R 2 , R 3 , and R 4 are alkyl groups, with at least one of R 1 , R 2 , R 3 , and R 4 being an alkyl group having at least ten carbon atoms; and A − is a counter anion; and
(iii) phenyl-C61-butyric acid methyl ester that is covalently bound by an amide bond, in place of the ester group, via a linker to the surface of the hollow spherical silica particles.
2. The insulating composition of claim 1 , wherein said coating material is polystyrene.
3. The insulating composition of claim 1 , wherein said coating material is polyvinylpyrrolidone.
4. The insulating composition of claim 1 , wherein said coating material is said quaternary ammonium salt having the formula (1).
5. The insulating composition of claim 4 , wherein said quaternary ammonium salt contains a cetyltrimethylammonium portion.
6. The insulating composition of claim 1 , wherein said coating is material phenyl-C61-butyric acid methyl ester that is covalently bound by an amide bond, in place of the ester group, via a linker to the surface of the hollow spherical silica particles.
7. The insulating composition of claim 1 , wherein said hollow spherical silica particles have a mean particle size of up to 1000 nm.
8. The insulating composition of claim 1 , wherein said hollow spherical silica particles have a mean particle size of up to 500 nm.
9. The insulating composition of claim 1 , wherein said hollow spherical silica particles do not contain surface porosity.
10. The insulating composition of claim 1 , wherein said hollow spherical silica particles contain surface porosity.
11. The insulating composition of claim 10 , wherein said surface porosity is characterized by pores having a size of up to 50 nm.
12. The insulating composition of claim 10 , wherein said surface porosity is characterized by pores having a size of up to 10 nm.
13. The insulating composition of claim 10 , wherein said surface porosity is characterized by pores having a size of up to 5 nm.
14. The insulating composition of claim 10 , wherein said surface porosity is characterized by pores having a size of up to 1 nm.
15. A method of thermally insulating a surface, the method comprising applying a coating of a thermally insulating composition onto said surface, wherein said thermally insulating composition comprises hollow spherical silica particles and a coating material having a thermal conductivity of less than 0.3 W/m·K on surfaces of said hollow spherical silica particles, wherein said coating material is selected from at least one of the following:
(i) polymers selected from polystyrene or polyvinylpyrrolidinone;
(ii) quaternary ammonium salt having the following formula:
wherein R 1 , R 2 , R 3 , and R 4 are alkyl groups, with at least one of R 1 , R 2 , R 3 , and R 4 being an alkyl group having at least ten carbon atoms; and A − is a counter anion; and
(iii) phenyl-C61-butyric acid methyl ester that is covalently bound by an amide bond, in place of the ester group, via a linker to the surface of the hollow spherical silica particles.
16. The method of claim 15 , wherein said coating material is polystyrene.
17. The method of claim 15 , wherein said coating material is polyvinylpyrrolidone.
18. The method of claim 15 , wherein said coating material is said quaternary ammonium salt having the formula (1).
19. The method of claim 18 , wherein said quaternary ammonium salt contains a cetyltrimethylammonium portion.
20. The method of claim 15 , wherein said coating material is phenyl-C61-butyric acid methyl ester that is covalently bound by an amide bond, in place of the ester group, via a linker to the surface of the hollow spherical silica particles.
21. The method of claim 15 , wherein said hollow spherical silica particles have a mean particle size of up to 1000 nm.
22. The method of claim 15 , wherein said hollow spherical silica particles have a mean particle size of up to 500 nm.
23. The method of claim 15 , wherein said hollow spherical silica particles do not contain surface porosity.
24. The method of claim 15 , wherein said hollow spherical silica particles contain surface porosity.
25. The method of claim 24 , wherein said surface porosity is characterized by pores having a size of up to 50 nm.
26. The method of claim 24 , wherein said surface porosity is characterized by pores having a size of up to 10 nm.
27. The method of claim 24 , wherein said surface porosity is characterized by pores having a size of up to 5 nm.
28. The method of claim 24 , wherein said surface porosity is characterized by pores having a size of up to 1 nm.